The present invention relates to gas valves; more particularly, the invention relates to a gas valve having a diaphragm closure member, wherein the valve is structured to eliminate contaminants from the gas flow path.
Contaminant-free gas valves have application in use in systems for handling high purity, reactive and hazardous gases. Such applications are typically found in specialty gas handling equipment, process gas purge panels and manifolds, compressed gas cylinder cabinets, gas analysis and sampling equipment, chromatography equipment and instrumentation and research equipment. In such applications it is desirable, and sometimes absolutely critical, to provide a volume flow of gas wherein no contaminant materials are introduced into the gas flow volume by any components in the flow system, particularly movable and adjustable valves. It is known that contaminants are produced by valve seal components having pliable characteristics, wherein minute particles of the valve seal material may break loose from the seal and enter into the gas flow path. It is also known that contaminants may be introduced into the gas flow path from other moving components in the valve chamber, such as the metal compression spring which is typically placed in the valve chamber. The metal spring exerts an opening force in opposition to an externally-driven actuating member, and contaminant particles may break away from the spring over extended use. Such particles may include various metal oxides, plating components, and other particulate matter.
It is therefore desirable to provide a gas flow system wherein all of the interior components and surfaces which are directly exposed to the gas flow stream are free from contaminants, or are entirely non-reactive with the gases flowing through the system. It is relatively easy to design a gas flow system wherein the fixed components are constructed from materials which meet the non-contaminating and non-reactive standards. It is somewhat more difficult to design components which have moving or movable parts to be free from contaminating or reacting with the gas. In particular, the materials which usually make the most effective valve seals also have a propensity to release contaminants into the gas flow stream. Even valve springs, which may be made from non-reactive metallic materials, can become a source of contaminants through extended use. Contact with reactive gases in the flow path may result in the buildup of surface oxides on the springs, and oxide particulates may break away from the spring and enter the flow path. Continuous and extensive operation of a spring may result in the release of particulates either from the spring plating materials or from the spring base material.